Do I need to add supplements to complete dry food?

Usually no — complete food is already balanced. Here is the reasoning behind that answer, and the exceptions worth knowing.

The short answer

Usually no — complete food is already balanced.

Adding calcium, oils or vitamins on top of a complete diet unbalances it. Exceptions are vet-diagnosed joint disease, skin conditions or pregnancy, and those should be dosed, not guessed.

Why it works that way

Feeding decisions compound: a 10% overshoot becomes 2–3 kg a year, and joint disease follows weight rather than age. That is why portion control and body condition scoring outrank brand loyalty in every credible feeding guideline.

• Weigh food rather than scooping by eye for at least two weeks.
• Score body condition monthly using ribs, waist and belly tuck.
• Change one variable at a time so you can tell what worked.

When to ask your vet instead

See a vet rather than adjusting diet if you notice weight loss without diet change, persistent loose stools, vomiting, or a sudden refusal to eat. Those are clinical signs, not feeding problems.

Adjust slowly, measure consistently, and let body condition be the referee.